1. Field of the Invention
This invention relates to a magnetic tape driving device for a tape recorder or like machines.
2. Description of the Prior Art
Magnetic tape driving devices for tape recorders or like machines conventionally employ a base plate formed from a metal plate. However, it has been also attempted to form such a base plate partially from a synthetic resin material. This allows reduction of the quantity of parts and the production costs of tape recorders because part mounting portions or pieces for mounting a number of parts, guide portions and the like can be integrally formed on such a synthetic resin portion.
However, where a base plate of a magnetic tape driving device is partially made of a synthetic resin material, the base plate has a reduced mechanical strength and a greater thermal deformation at the synthetic resin portion thereof. Accordingly, if a bearing metal member for supporting a capstan thereon is mounted only on the synthetic resin portion, this will cause a problem that the capstan may be slanted due to deformation of the synthetic resin portion or vibrations upon rotation of the capstan may increase and cause a phenomenon or resonance, which will extremely deteriorate the wow and flutter characteristic of the tape recorder.
Further, where the bearing metal member is held only by the synthetic resin portion, there is a drawback that because the bearing metal member is electrically insulated from the metal plate portion of the base plate, when the capstan is rotated at a high speed, a magnetic tape may coil around the capstan or electrostatic noises may be produced under the influence of static electricity generated by mutual contact betwen the capstan and the bearing metal member.
Therefore, in a magnetic tape driving device in which part of a tape recorder base plate is formed from a synthetic resin material, it is necessary to interconnect a bearing metal member for a capstan and a metal plate portion of the base plate by means of an earthing line in order to establish a conducting condition between them. Accordingly, it is a problem that a production step is increased for connection of such an earthing line and the production cost is increased accordingly.